You may want to verify the overall path to the file or folder that you are copying is actually within the limiation of 255 characters or less. If it's more than 255 characters, you may want to rename some of it's parent folder to make it within 255 characters.

what about the folder under \\machinename\foldername\foldername1\Files? could there be another folders after the folder "Files"? If not and only files, the that shouldn't be more than 255 character for your UNC path, unless the filename under "Files" is very long.

Also, the file or folder that you cannot copy, can you see the NTFS(Security) permission?

Try unchecking "Allow the computer to turn off this device to save power" in the NIC's Power Management tab. That should eliminate your problem with the network path.
As Americom states, it also seems like the path is too long. You could use xcopy from the command line to copy the files. There's a switch to continue copying on errors as in:
xcopy \\server\share\*.* c:\folder /E /C /Y
This copies everything from the shared drive to c:\folder drive, continues on errors, and suppresses the prompt to overwrite existing files
run xcopy /? to see all switches

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